Spatial and Temporal Distribution of Surface Ozone in the White Mountains

Surface ozone concentrations were measured at Owens Valley Laboratory plus four additional high-elevation sites in the White Mountains: USFS Cabins (near the CARMA radio-telescope array), Crooked Creek Station, Barcroft Station, and White Mountain Summit. Data collection at the non-summit sites commenced on June 9-10 and concluded on October 16-18. Measurements at White Mountain Summit started somewhat later, on July 14, and an early-season snowstorm prevented retrieval of the summit-based ozone monitor. High daytime concentrations of ozone (~50 ppb) were observed at all locations, with minimal diurnal variation (approximately ±5 ppb or less) in the measurements at White Mountain Summit, Barcroft Station, and the USFS Cabins. Crooked Creek and Owens Valley Laboratory displayed significantly larger diurnal variability, with early morning minima near 35 ppb and 15-20 ppb, respectively, for these two locations. It is hypothesized that the highest elevation sites with the best exposure to the open atmosphere – White Mountain Summit and Barcroft Station – sampled “background” tropospheric ozone levels that were unperturbed by local production or destruction mechanisms. The other sites, located at lower elevations – and/or with less exposure to the open atmosphere – experienced greater levels of dry deposition of ozone during evening hours, resulting in more pronounced diurnal variations.